JPH0691299A - Method for treating drainage and apparatus therefor - Google Patents

Abstract

PURPOSE:To eliminate residual ozone efficiently and to improve biological treatment in a later step by a method in which drainage to be treated, after being contacted with ozone countercurrently, is added with a part of untreated drainage to eliminate the residual ozone. CONSTITUTION:In an ozone contact tower 1, drainage to be treated which is introduced from the upper part through pipes 11, 12, countercurrently contacts ozone introduced from the lower part through an ozone introduction pipe 1A, and the treated drain is discharged through a pipe 14 at the bottom. In the ozone treatment range in the contact tower 1, the oxidation-treated drainage is added with a part of untreated drainage. The residual ozone in the treated drainage is consumed during the oxidation of organic materials diffical to decompose in the untreated drainage to be eliminated effectively. The treated drainage after the elimination of its residual ozone is led to a biological reaction tank 2 through a pipe 14 and separated biologically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method and a wastewater treatment apparatus, and more particularly to a wastewater treatment method for stably and efficiently decomposing hardly decomposable organic substances by using a combination of ozone oxidation treatment and biological treatment. Related to wastewater treatment equipment.

[0002]

2. Description of the Related Art Conventionally, as a method for removing hardly decomposable organic substances in waste water, there has been known a method in which the hardly decomposable organic substances are converted into biodegradable organic substances by ozone oxidation and then decomposed and removed by a biological reaction. ing. In particular, in the field of water purification, a method has been adopted in which, by using activated carbon (biological activated carbon) as a filler in a biological reaction tank, organic substances are efficiently removed by a combined effect with physical adsorption of activated carbon.

By the way, the solubility of ozone in water is
It is several times to ten times as large as oxygen, which is why
In the ozone-treated water that has been subjected to the ozone oxidation treatment, it generally varies from 0.1 to several meters, although it varies depending on the ozone treatment conditions.
It contains g / l of residual ozone.

Ozone contained in ozone-treated water has a strong inactivating effect on microorganisms in the biological treatment in the subsequent step and inhibits biological reactions. For example, the residual ozone concentration of 0.
There are also reported cases where general bacteria were sterilized by 99% at 29 mg / l or less.

Therefore, in order to favorably perform the biological treatment after the ozone treatment, it is necessary to remove residual ozone in the ozone-treated water by some method prior to the biological treatment.

Conventionally, as a general ozone removal method, high p
H self-decomposition method of ozone, reducing agent such as sodium sulfite, stripping method by aeration, or
There is a method of staying for a long time.

[0007]

However, all of the above ozone removal methods require chemicals, or
It cannot be used for wastewater treatment due to problems such as slow removal rate and impracticality.

On the other hand, in the case of a biological treatment tank using biological activated carbon, residual ozone in ozone-treated water is adsorbed and decomposed, but in this case, expensive activated carbon is required as a biological filler and activated carbon is also used. After the physical adsorption capacity of is saturated,
No adsorption effect can be obtained.

In this case, although the activated carbon is expensive, it merely functions as a filler for retaining microorganisms, and an effect commensurate with the cost of the filler cannot be obtained.

The present invention solves the above-mentioned conventional problems, and when the wastewater is subjected to the ozone oxidation treatment and then biological treatment, the residual ozone in the ozone-treated water does not depend on the chemical addition or the adsorption effect of the activated carbon, and does not require a large scale. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus capable of enhancing biological treatment efficiency and stabilizing treatment by efficiently removing the wastewater without requiring equipment.

[0011]

A method for treating wastewater according to claim 1 is a method of biologically treating the wastewater to be treated in a countercurrent contact with ozone, wherein the ozone-treated water after contact with ozone is It is characterized by adding a part of the wastewater to be treated.

The method for treating wastewater according to claim 2 is the method according to claim 1, wherein a residual ozone concentration in the mixed water obtained by adding a part of the wastewater to be treated to the ozone-treated water is measured. Based on the above, the amount of treated wastewater to which ozone-treated water is added is increased or decreased.

According to a third aspect of the wastewater treatment apparatus, the wastewater to be treated is introduced from the upper drainage inlet and the ozone is introduced from an ozone inlet below the wastewater inlet to separate the wastewater to be treated and the ozone. An ozone contact tower that is treated by contacting in countercurrent and is treated so that water after ozone treatment is extracted from a lower outlet, and a biological treatment tank that receives the ozone-treated water extracted from the ozone contact tower and biologically treats it. In the wastewater treatment device having the above, the wastewater introduction means for introducing a part of the wastewater to be treated into the ozone contact tower from a portion between the ozone inlet and the outlet of the ozone contact tower is provided. To do.

According to a fourth aspect of the wastewater treatment apparatus, an ozone contact tower for countercurrently contacting the wastewater to be treated with ozone, a deozone tank into which the ozone-treated water from the ozone contact tower is introduced, and the deozone tank. Wastewater injecting means for injecting a part of the wastewater to be treated into a communication path between the ozone contact tower and the deozonation tank or the deozonation tank. It is characterized by having.

[0015]

The relationship between ozone and persistent organic matter (COD) in untreated wastewater in the ozone contact tower can be considered as follows.

[0016]

[Chemical 1]

That is, the gaseous ozone is first dissolved in the liquid, and the dissolved ozone in the liquid (or radicals generated from it) participates in the COD oxidation reaction. Therefore, whether or not ozone remains in the liquid depends on the magnitude of the _two reaction rates (K ₁ , K ₂ ). A general decomposition pattern of COD by ozone is shown in FIG. COD decreases as the ozone injection rate increases, but its reaction rate is
Gradually decreases. Therefore, when the ozone injection rate is small,
K ₁ <K ₂ , and no ozone remains in the liquid. However, when the ozone injection rate becomes large, K ₁ > K ₂ , and ozone remains. As the operating conditions of the ozone contact tower, there may be a case where ozone does not remain, but in general, ozone often remains in the liquid.

When a part of the untreated wastewater is added to the ozone-treated water according to the present invention, the residual ozone is preferentially utilized among the COD contained in the untreated wastewater having a high reaction rate with ozone. By consuming the carbon dioxide for the oxidative decomposition of COD, the residual ozone can be removed in a short time. Moreover, since the untreated wastewater is used to remove the residual ozone, the utilization efficiency of ozone is also improved as a result.

According to the method of claim 2, the amount of untreated wastewater added to the ozone-treated water can be automatically controlled to the optimum amount.

According to the wastewater treatment equipment of the third aspect, the wastewater treatment method of the present invention can be easily carried out with simple equipment.

According to the wastewater treatment equipment of claim 4, the residual ozone can be removed more efficiently.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

1, 2, and 3 are system diagrams showing an embodiment of the wastewater treatment apparatus of the present invention, in which 1 is an ozone contact tower equipped with an ozone inlet pipe 1A, 2 is a biological reaction tank, 3 is a deozone tank, 4 is an ozone meter, 5 is a valve, 11 and 1
2, 13, 14, 14A, 14B and 15 are pipes.

In the following, adding a part of raw water to ozonated water may be referred to as "dispensing", and the ratio of the amount of raw water to be dispensed to the total amount of raw water may be referred to as "dispensing amount". .

The waste water treatment apparatus of FIG. 1 comprises an ozone contact tower 1 for ozone treatment of raw water introduced through pipes 11 and 12,
The biological treatment tank 2 biologically treats the ozone-treated water introduced from the pipe 14 and discharges it from the system through the pipe 15.

In the ozone contact tower 1, raw water (untreated wastewater) introduced from the upper portions of the pipes 11 and 12 is in countercurrent contact with ozone introduced from the lower ozone introduction pipe 1A, and the ozone treated water is of the bottom portion. A part of the raw water is discharged from the pipe 14, and through the pipe 13 branched from the pipe 11, a part of the raw water is below the ozone introducing pipe 1A of the ozone contact tower 1 and above the discharge pipe 14 of the ozone-treated water. It is configured to be introduced in the position.

With such a device, the ozone contact tower 1
Part of the raw water is added from the pipe 13 to the ozone-treated water that has been subjected to the ozone oxidation treatment in the ozone-treated region (in the figure, the region in the ozone contact tower 1 above the ozone introduction pipe 1A). The residual ozone is consumed for the oxidation of the persistent organic matter in the raw water, while no new ozone is blown below the raw water addition part, so the residual ozone in the ozonated water is efficiently removed. To be done.

Thus, the ozone-treated water from which the residual ozone has been removed is introduced into the biological reaction tank 2 through the pipe 14 and efficiently biodegraded.

In the present invention, a part of the raw water to be dispensed is made to flow directly into the lower part of the ozone contact tower as shown in FIG. 1 or to the ozone-treated water discharge pipe 14 of the ozone contact tower 1. Is also good.

Further, in this case, as shown in FIG. 3, a deozone tank 3 is provided in the middle of the ozone discharge pipe, and a part of the raw water is added to the ozone-treated water discharged from the pipe 14A to obtain the mixed water. May be retained in the deozone tank 3 for a predetermined period of time to sufficiently remove ozone, and then fed to the biological treatment tank 2 through the pipe 14B.

In this case, the raw water is dispensed as
It may be directly carried out to the ozone removal tank 3.

In the present invention, the amount of the raw water dispensed may be small, and strictly speaking, it depends on the residual ozone concentration of the ozone-treated water and the COD concentration of the raw water, but in general, 1 /
A sufficient effect can be obtained with a dispensed amount of about 10 to 1/100.

When controlling the dispensed amount from the residual ozone concentration in the ozone-treated water and the COD concentration of the raw water,
As shown in FIG. 4, if the ozone meter 4 is provided in the ozone-treated water discharge pipe 14 and the valve 5 is provided in the raw water dispensing pipe 13, the opening and closing of the valve 5 is adjusted based on the measured value of the ozone meter 4. good. According to the apparatus of FIG. 4, the dispensed amount can be automatically controlled, and residual ozone can be removed stably and reliably. In this case, if the COD concentration of the raw water varies, a COD concentration measuring means for the raw water is further provided, and from this measurement value and the measurement value of the ozone meter,
A more reliable process can be performed by calculating an appropriate dispensing amount and controlling the dispensing amount based on the calculation result.

The present invention can be effectively applied to each apparatus unit even when a plurality of processing apparatus units each consisting of an ozone contact tower and a biological reaction tank are connected in series to perform multi-stage processing.

The present invention will be described in more detail with reference to specific examples.

Example 1 Using the treated sludge sludge treated water of beer manufacturing wastewater as raw water, treatment was carried out under the following treatment conditions in the apparatus shown in FIG.

Raw water injection rate : 5% Ozone contact tower : HRT = 20 minutes Blow ozone gas concentration = 20 ppm Ozone gas blow rate = 50 ml / min Deozone tank HRT = 1 minute Biological reaction tank Filler = Ceramic particles (mesh 10 / 32) HRT = 20 minutes COD concentration of raw water, ozonated water and biological treated water
Shown in.

Comparative Example 1 The same treatment as in Example 1 was carried out except that the raw water was not dispensed. Table 1 shows the COD concentrations of raw water, ozone-treated water, and biologically-treated water.

COMPARATIVE EXAMPLE 2 A deozone tank was not provided, and activated carbon particles (mesh 10/3) were used instead of ceramic particles as a filler for the biological reaction tank.
The same treatment as in Comparative Example 1 was performed except that 2) was used. Table 1 shows the COD concentrations of raw water, ozone-treated water, and biologically-treated water.

[0040]

[Table 1]

The following is clear from Table 1. In Example 1, the raw water was dispensed to remove the residual ozone in the ozone-treated water. Therefore, it is possible to efficiently perform biological treatment using an inexpensive filler and obtain treated water having a low COD concentration. On the other hand, in Comparative Example 1 in which the raw water is not dispensed, the residual ozone in the ozone-treated water inhibits the biological treatment, and thus the COD concentration of the obtained treated water is high.

On the other hand, in Comparative Example 2 in which activated carbon is used as the filler for the biological reaction tank, the activated carbon adsorbs and removes the residual ozone in the ozone-treated water, so that biological treatment is not hindered. When activated carbon is used, CO
D is adsorbed and removed on the activated carbon, and a lower treated water COD concentration is obtained, but after about 2 months, this adsorption reaches saturation,
The quality of the treated water is the same as in Example 1. Therefore, in this case, the expensive activated carbon only functions as a carrier for holding organisms, which is economically disadvantageous.

[0043]

As described above in detail, according to the wastewater treatment method of the present invention, residual ozone in ozone-treated water can be removed easily, efficiently and inexpensively in a short time without using chemicals. Therefore, it is possible to stably maintain the microorganisms in the biological treatment in the subsequent step, enhance the biological treatment efficiency, and stabilize it. Moreover, the ozone utilization efficiency in the ozone treatment can be improved. Further, since it is not necessary to use expensive activated carbon as a filling material for the biological reaction tank, the processing cost becomes extremely low.

According to the method of claim 2, the amount of untreated wastewater added to the ozone-treated water can be automatically controlled to the optimum amount.

According to the wastewater treatment equipment of the third aspect, the wastewater treatment method of the present invention can be easily carried out with simple equipment.

According to the wastewater treatment equipment of claim 4, the residual ozone can be removed more efficiently.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a wastewater treatment device of the present invention.

FIG. 2 is a diagram showing a decomposition pattern of COD with ozone.

FIG. 3 is a system diagram showing another embodiment of the waste water treatment apparatus of the present invention.

FIG. 4 is a system diagram showing another embodiment of the wastewater treatment equipment of the present invention.

[Explanation of symbols]

 1 ozone contact tower 2 biological reaction tank 3 deozone tank

Claims (4)

[Claims] 1. A method for biological treatment after contacting treated wastewater with ozone countercurrently, wherein a part of the treated wastewater is added to ozone-treated water after contact with ozone. Wastewater treatment method. 2. The method according to claim 1, wherein a residual ozone concentration in the mixed water obtained by adding a part of the wastewater to be treated to the ozone-treated water is measured, and the residual ozone concentration is measured based on the measured value. A method for treating wastewater, characterized by increasing or decreasing the amount of wastewater to be added. 3. The treated wastewater is introduced from an upper drainage inlet, and the ozone is introduced from an ozone inlet below the wastewater inlet to treat the treated wastewater and ozone in countercurrent contact. In an effluent treatment device having an ozone contact tower adapted to extract water after ozone treatment from a lower outlet, and a biological treatment tank for biologically treating by receiving the ozone-treated water extracted from the ozone contact tower, A wastewater treatment device comprising a wastewater introducing means for introducing a part of wastewater to be treated into the ozone contact tower from a portion between an ozone inlet and an outlet of the ozone contact tower. 4. An ozone contact tower for countercurrently contacting treated wastewater and ozone, a deozonation tank into which ozone-treated water from the ozone contact tower is introduced, and deozonated water from the deozonation tank A biological treatment tank to be introduced, and a drainage injection means for injecting a part of the wastewater to be treated into a communication path between the ozone contact tower and the deozonation tank or the deozonation tank. Wastewater treatment equipment.